Apparatus for the concentration of acids



Aug. 27, 1940. c. 1.. JONES APPARATUS FOR THE CONCENTRATION OF ACIDS Filed May 10, 1938 OUTLET 5 TEAM INLE T 6 5/6/77 GL/LSS E 5/ WP ACID //VLE'7' MA fiham g FIG. 1

Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE APPARATUS FOR THE CONCENTRATION OF ACIDS Application May 10, 1938, Serial No. 206,991

3 Claims.

This invention relates to aprocess of concentrating dilute mineral acids, and more particularly to a process of concentrating dilute sulfuric acid.

Heretofore, it has been the practice to evaporate dilute mineral acids, such as sulfuric or phosphoric acids, at atmospheric or reduced pressures, in apparatus composed of cast iron, siliconiron alloys, or fused quartz. The use of any of these materials of construction leads to difliculties and high costs.

Cast iron, while in general resistant to corrosion by very hot, evaporating acids, is'subject to attack by them and has a comparatively short life. In addition, cast iron always contains pores,

or pockets, into which the acid penetrates forming iron sulfate which exerts a pressure on the walls surrounding the pocket, and causes the cast iron vessel to crack. Moreover, the attack by the acid causes the concentrated acid to be contaminated by relatively large quantities of iron sulfate.

Silicon-iron alloys, while far more resistant to corrosion than cast iron, in the concentration of acids, are, however, extremely brittle and fragile, can only be cast, and cannot be machined except by grinding. Their fragile nature renders pipes made of this material a source of danger from. cracking, either from expansion or from internal pressure, and the use of high'pressures within such tubes extremely hazardous.

Fused quartz is objectionable, not only because of its very high cost, but also on account of its glass-like brittleness.

With only the above materials of construction available, the art of concentrating high-boiling mineral acids has suffered severe handicaps.

Recently,,there has come into extended use the vacuum type of acid concentrator, wherein a body of dilute acid, confined in a tank having an acid resistant lining, is subjected to vacuum and heated by immersed pipes comprised of siliconiron alloy, through which pipes is passed a heating'medium under pressure, for example heated oil or steam.

This type of apparatus is very economical and eflicient, but suffers from the handicap of the danger of cracking of the silicon-ironalloy by tubes used to heat the acid. As stated, such tubes are very brittle, and if they crack, while filled with steam under pressure, the steam blows'into the more or less concentrated acid, with very disturbing and dangerous results, to say the least. Moreover, since the tensile strength of the siliconiron alloy tubes is very low, the use of high pressure steam, with the attendant advantage of higher temperature, is impossible.

The object of this invention is to provide a vacuum concentrating apparatus, adaptedsafely and efilciently to concentrate high-boiling mineral acids, which will obviate the dangers of breakage of heating pipes and the dangers of leakage of the heating medium into hot, more or less concentrated mineral acid.

For the purpose of illustrating my invention, reference is made to the accompanying drawing, in Figure 1 of which I represents an upright section of a metal container, preferably lined with an acid-proof lining 2, for example, of acid-proof brick set in silicate cement, said vessel having within it a quantity of dilute acid to be concentrated, 3 represents a jet pump or the like, operated by steam from pipe 4, for the purpose of producing in the space within vessel l a vacuum, 4' various steam supply pipes, 5 sight glasses, 6 closed end metal tubes composed of an alloy consisting of nickel about 85%, silicon about 10%, aluminum about 2%, and copper about 3%, and 1 an opening in the vessel through which dilute acid may be fed in via valve 8, or through which concentrated acid may escape via valve 9.

Figure 2 of the accompanying drawing is a plan view of the apparatus of Figure 1, in partial cross section.

The alloy of which my steam tube is comprised has a tensile strength of from 36,000- 40,500 lbs. per square inch, compared to about 16,000 lbs. per square inch for silicon-iron alloy,

a transverse breaking strength of 5000 lbs. for a 1 inch square on a 12 inch span, as compared to 1260 lbs. for a silicon-iron alloy, and I have What I claim and desire to protect by Letters 45 Patent-rise 1.--Apparatus for concentrating acids comprising, in combination, an acid-proof vessel, means for producing vacuum within said vessel, means for feeding in and removing acid from said vessel, heating tubes extending within said vessel and consisting of an alloy consisting of about 85% nickel, about 10% silicon, about 2% aluminum, and about 3% copper.

2. Apparatus for concentrating acids comprising, in combination, an acid-proof vessel, means ing, in combination, an acid-proof vessel, means for producing vacuum within said vessel, means for feeding in and removing acid from said vessel, heating tubes extending radially within said vessel and consisting of an alloy of about 85% nickel, about 10%silicon, about 2% aluminum, and about 3% copper, and means for circulating steam through said heating tubes.

CHARLES L. JONES. 

